Of course, I do have a cow vertebrae and a squirrel skeleton in my tank, both real!
I don't mind decor in the tank besides fake plants. To me the skulls just seem to stand out to much. If you could make them not so bright or put moss or fissedens. It might make it not stand out so much.
They will darken, just like the croc one did. I have java moss near both, hoping that it will take to it.
Have an idea, of course it would mean rescaping the tank, and will post in new thread. Looking into some type of temple/mayan/indiana jones feel to it. Gonna need ideas though lol. I think doing something like that will let me really incorporate the skulls, but make them more a part of the tank, rather than a distraction.